This section is intended to provide a background or context to the invention that is recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived, implemented or described. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.
The following abbreviations that may be found in the specification and/or the drawing figures are defined as follows:    3GPP third generation partnership project    BS base station    BSR buffer status report    BW bandwidth    CA carrier aggregation    CC component carrier    CE control element    CQI channel quality indicator    DL downlink (eNB towards UE)    eNB E-UTRAN Node B (evolved Node B)    EPC evolved packet core    E-UTRAN evolved UTRAN (LTE)    IMTA international mobile telecommunications association    ITU-R international telecommunication union-radiocommunication sector    LCG logical channel group    LTE long term evolution of UTRAN (E-UTRAN)    LTE-A LTE advanced    MAC medium access control (layer 2, L2)    MCS modulation coding scheme    MIMO multiple input/multiple output    MM/MME mobility management/mobility management entity    NodeB base station    OFDMA orthogonal frequency division multiple access    OAM operations and maintenance    PDCCH physical downlink control channel    PDCP packet data convergence protocol    PDU protocol data unit    PHR power headroom report    PHY physical (layer 1, L1)    Rel release    RLC radio link control    RLF radio link failure    RRC radio resource control    RRM radio resource management    SC-FDMA single carrier, frequency division multiple access    SCH shared channel    SGW serving gateway    TTI transmission time interval    UE user equipment, such as a mobile station, mobile node or mobile terminal    UL uplink (UE towards eNB)    UTRAN universal terrestrial radio access network
One modern communication system is known as evolved UTRAN (E-UTRAN, also referred to as UTRAN-LTE or as E-UTRA). The DL access technique is OFDMA, and the UL access technique is SC-FDMA.
One specification of interest is 3GPP TS 36.300, V8.11.0 (2009-12), “3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Access Network (EUTRAN); Overall description; Stage (Release 8),” incorporated by reference herein in its entirety. This system may be referred to for convenience as LTE Rel-8. In general, the set of specifications given generally as 3GPP TS 36.xyz (e.g., 36.211, 36.311, 36.312, etc.) may be seen as describing the Release 8 LTE system. More recently, Release 9 versions of at least some of these specifications have been published including 3GPP TS 36.300, V9.1.0 (2009-9).
FIG. 1A reproduces FIG. 4.1 of 3GPP TS 36.300 V8.11.0, and shows the overall architecture of the EUTRAN system (Rel-8). The E-UTRAN system 2 includes eNBs, providing the E-UTRAN user plane (PDCP/RLC/MAC/PHY) and control plane (RRC) protocol terminations towards the UE (not shown). The eNBs are interconnected with each other by means of an X2 interface. The eNBs are also connected by means of an S1 interface to an EPC, more specifically to a MME by means of a S1 MME interface and to an S-GW by means of a S1 interface (MME/S-GW 4). The S1 interface supports a many-to-many relationship between MMEs/S-GWs and eNBs.
The eNB hosts the following functions:
functions for RRM: RRC, Radio Admission Control, Connection Mobility Control, dynamic allocation of resources to UEs in both UL and DL (scheduling);
IP header compression and encryption of the user data stream;
selection of a MME at UE attachment;
routing of User Plane data towards the EPC (MME/S-GW);
scheduling and transmission of paging messages (originated from the MME);
scheduling and transmission of broadcast information (originated from the MME or OAM); and
a measurement and measurement reporting configuration for mobility and scheduling.
Also of interest herein are the further releases of 3GPP LTE (e.g., LTE Rel-10) targeted towards future IMTA systems, referred to herein for convenience simply as LTE-Advanced (LTE-A). Reference in this regard may be made to 3GPP TR 36.913, V9.1.0 (2009-12), 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Requirements for Further Advancements for EUTRA (LTE-Advanced) (Release 9), incorporated by reference herein. A goal of LTE-A is to provide significantly enhanced services by means of higher data rates and lower latency with reduced cost. LTE-A is directed toward extending and optimizing the 3GPP LTE Rel-8 radio access technologies to provide higher data rates at lower cost. LTE-A will be a more optimized radio system fulfilling the ITU-R requirements for IMT-Advanced while keeping backwards compatibility with LTE Rel-8.
As is specified in 3GPP TR 36.913, LTE-A should operate in spectrum allocations of different sizes, including wider spectrum allocations than those of LTE Rel-8 (e.g., up to 100 MHz) to achieve the peak data rate of 100 Mbit/s for high mobility and 1 Gbit/s for low mobility. It has been agreed that carrier aggregation is to be considered for LTE-A in order to support bandwidths larger than 20 MHz. Carrier aggregation, where two or more component carriers (CCs) are aggregated, is considered for LTE-A in order to support transmission bandwidths larger than 20 MHz. The carrier aggregation could be contiguous or non-contiguous. This technique, as a bandwidth extension, can provide significant gains in terms of peak data rate and cell throughput as compared to non-aggregated operation as in LTE Rel-8.
A terminal may simultaneously receive one or multiple component carriers depending on its capabilities. A LTE-A terminal with reception capability beyond 20 MHz can simultaneously receive transmissions on multiple component carriers. A LTE Rel-8 terminal can receive transmissions on a single component carrier only, provided that the structure of the component carrier follows the Rel-8 specifications. Moreover, it is required that LTE-A should be backwards compatible with Rel-8 LTE in the sense that a Rel-8 LTE terminal should be operable in the LTE-A system, and that a LTE-A terminal should be operable in a Rel-8 LTE system.
FIG. 1B shows an example of CA, where M Rel-8 component carriers are combined together to form MHRe1-8 BW (e.g. 5 H 20 MHz=100 MHz given M=5). Rel-8 terminals receive/transmit on one CC, whereas LTE-A terminals may receive/transmit on multiple CCs simultaneously to achieve higher (wider) bandwidths.
Basically, in CA it is possible to configure a UE to aggregate a different number of CCs originating from the same eNB, of possibly different BWs, in the UL and the DL. Rel-8 UEs are assumed to be served by a single stand-alone CC, while Release 10 (LTE-A) terminals can be configured to receive or transmit simultaneously on multiple aggregated CCs in the same TTI.
As is currently specified for LTE, one subframe is equal to one millisecond, and comprises two 0.5 millisecond slots.
In addition, configured CCs can be de-activated in order to reduce the UE power consumption. In this case the UE monitoring activity of a de-activated carrier is reduced (e.g., no PDCCH monitoring and CQI measurements are needed). This mechanism can be referred to as carrier activation/deactivation.
Furthermore, to assist the eNB scheduler functionality the eNB can configure UEs to send BSRs and PHRs in the UL. Reference in this regard can be made to 3GPP TS 36.321 V9.1.0 (2009-12) Technical Specification 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA) Medium Access Control (MAC) protocol specification (Release 9), such as in Section 5.4.5 “Buffer Status Reporting” and Section 5.4.6 “Power Headroom Reporting”.
The BSR indicates the amount of data the UE has available for transmission, while the PHR provides the eNB with information about the difference between the nominal UE maximum transmit power and the estimated power for UL-SCH transmission. BSRs are typically used by the eNB to select an appropriate transport block size, while PHRs are typically used to select an appropriate MCS.
BSRs are sent by the UE in the UL in the form of Buffer Status Report MAC Control Elements (see 3GPP TS 36.321, Section 6.1.3.1, “Buffer Status Report MAC Control Elements”) in which the Buffer Size (BS) field identifies the total amount of data available for transmission. The length of this field is specified as 6 bits and contains exponentially distributed buffer size levels based on a minimum buffer size level (Bmin), a maximum buffer size level (Bmax) and a number of reported buffer size levels (N).
Reference can be made, for example, to R2-083101, “Buffer Size Levels for BSR in E-UTRA Uplink”, 3GPP TSG-RAN WG2 Meeting #62bis, Warsaw, Poland, 30 Jun.-4 Jul. 2008, Source: Ericsson, Nokia Corporation, Nokia Siemens Networks, Samsung.
FIG. 3A herein reproduces FIG. 6.1.3.1-1 of 3GPP TS 36.321 and shows a Short BSR and Truncated BSR MAC control element, FIG. 3B herein reproduces FIG. 6.1.3.1-2 of 3GPP TS 36.321 and shows a Long BSR MAC control element, and FIG. 3C herein reproduces Table 6.1.3.1-1 of 3GPP TS 36.321 and shows buffer size levels for BSR.
As is stated in 3GPP TS 36.321, Section 6.1.3.1, Buffer Status Report (BSR) MAC control elements consist of either the Short BSR and Truncated BSR format, with one LCG ID field and one corresponding buffer Size field (see FIG. 3A herein) or the Long BSR format having four buffer size fields, corresponding to LCG IDs #0 through #3 (see FIG. 3B herein). In a conventional sense the LCG is understood to be a group of UL logical channels for which a single joint buffer fill level is reported by the UE in a BSR. The mapping of logical channels to LCGs is defined by the eNodeB. The BSR formats are identified by MAC PDU subheaders with LCIDs as specified in table 6.2.1-2 (FIG. 3D herein). The fields LCG ID and Buffer Size are defined as follows. LCG ID: The Logical Channel Group ID field identifies the group of logical channel(s) for which buffer status is being reported. The length of the field is 2 bits. Buffer Size: The Buffer Size field identifies the total amount of data available across all logical channels of a logical channel group after the MAC PDU has been built. The amount of data is indicated as the number of bytes. It includes all data that is available for transmission in the RLC layer and in the PDCP layer. The size of the RLC and MAC headers are not considered in the buffer size computation. The length of this field is 6 bits. The values taken by the Buffer Size field are shown in Table 6.1.3.1-1 (FIG. 3C herein).
However, the BS field as specified for LTE Rel-8 and Rel-9 is based on the assumption that only one CC is used in the UL and, as a result, is not adequate for use with the higher data rates made possible by the use of CA in Rel-10 and beyond.